Styrene resin foam is lightweight, and is therefore used in various fields such as heat insulation applications such as home appliances and building materials, and civil engineering works applications such as embankment methods.
Styrene resin is composed of only carbon and hydrogen, and has a property of vigorously burning while emitting black smoke once igniting. Therefore, it is required to be flame-retarded by adding a flame retardant depending on its application. Bromine-containing compounds are widely used as such a flame retardant, and in order to impart high flame retardancy in a small addition amount, a flame retardant in which all of bromine atoms are bonded to aliphatic carbon, such as hexabromocyclododecane (HBCD), is effective. However, those flame retardants have low thermal stability, and induce the problems such as deterioration of a resin, coloration of a resin and corrosion of an apparatus due to generation of a hydrogen bromide gas. Furthermore, HBCD is hardly decomposable and has high bioaccumulation property. Therefore, reduction of the amount of HBCD used and development of an alternative flame retardant are required.
Tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) is proposed as a compound capable of giving the same level of flame retardancy in the same addition amount as HBCD (Patent Document 1). However, in recent years, it is required, due to increase in public eco-awareness, to again use a styrene resin foam once used or generated as an edge material by cutting when forming a product, as a raw material. In the use of such a recycled styrene resin foam, since a styrene resin foam already passed through a heating and melting step in the last production is used through further heating and melting, a thermal stability more than ever is required. It could not be said that the tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) has a sufficient thermal stability.
Tetrabromobisphenol-bis(2,3-dibromopropyl ether), tris(2,3-dibromopropyl)isocyanurate and the like are known as compounds having excellent thermal stability. However, flame-retardant effect is low as compared with a flame retardant such as HBCD, and it is required to greatly increase the addition amount. For this reason, there is a problem that not only physical properties of a styrene resin foam are deteriorated, but a cost of a styrene resin foam is greatly increased.